Because it doesn't provide solid flow all around the tank. Using lily pipes? Tiny amount of flow. Using a custom spray bar can help but there are still a ton of dead spots and circulation pumps are necessary.

My general rule of thumb: 2211 for 5gal or less, 2213 on nothing larger than 10gal, 2215 on 12-15, 2217 on 20-25.

I find the 2217 is perfect for a 20long. Seems to be consistent with what a lot of Planted Tank folks use.

Because it doesn't provide solid flow all around the tank. Using lily pipes? Tiny amount of flow. Using a custom spray bar can help but there are still a ton of dead spots and circulation pumps are necessary.

My general rule of thumb: 2211 for 5gal or less, 2213 on nothing larger than 10gal, 2215 on 12-15, 2217 on 20-25.

I find the 2217 is perfect for a 20long. Seems to be consistent with what a lot of Planted Tank folks use.

Im going to be using it on a 40 tall and am not worrying about the flow the filter will or will not be producing. im more or less looking to overfilter the tank on a higher level, ideally i want everything on the list of stocking that i said before, what would you recomend for a 40 tall?

I have a 2217 and a 2026 on my 120p, I broke my QD the 2026 and it was down for a week or so. The 2217 handled the tank just fine, I almost considered just getting a PW just for the co2 but I found a sale for the QD that I couldn't pass up.
IMO you will be fine with the 2217 for the time being, if you find you need more flow down the line just add a PW or go with another can if you can afford it.

A 2217 would not suffice for a 40g only if you are injecting CO2 and ferting regularly into the water column.

Otherwise, a 2217 is enough.

Instead of talking about flow, it's more prudent to understand why you need flow in the first place. It's not universally necessary or even preferable.

If you do need the high low, you don't need to get two 2217s. You can get a 2217 and a power head to increase flow. It's more mechanical clutter in your tank but much more affordable and less to maintain.

Also, there's no problem with turning your filter off and cleaning it. If your tank is established and not critically stocked, you'll be fine.

A 2217 would not suffice for a 40g only if you are injecting CO2 and ferting regularly into the water column.

Otherwise, a 2217 is enough.

Instead of talking about flow, it's more prudent to understand why you need flow in the first place. It's not universally necessary or even preferable.

If you do need the high low, you don't need to get two 2217s. You can get a 2217 and a power head to increase flow. It's more mechanical clutter in your tank but much more affordable and less to maintain.

Also, there's no problem with turning your filter off and cleaning it. If your tank is established and not critically stocked, you'll be fine.

Alright, the final moments before i order an Ehiem 2217, any last minute advice? i hear that you can get anaerobic bacteria in them, but my tank has good O2 levels so i dont believe i will encounter that issue.

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